Photoluminous copper(II)-2,2 '-dipyridylamine coordination frameworks: Two-dimensional superstructures based on hydrogen bonds and pi...pi/C-H...pi interaction

Treatment Of CU2(OAC)(4)-2H(2)O with 2,2'-dipyridylamine (dpa) in 1:2 molar ratio in MeCN-H2O results neutral (Cu(OAc)(2)(dpa)]-2H(2)O (1) which on subsequent treatment with 1 equiv of NaBF4 affords [Cu(OAc)(dpa)(2)]BF4 (2). The complexes are characterized using micro analytical, spectroscopic, magnetic, thermal, electrochemical, and other physicochemical results. Electrochemical electron transfer study of 1 and 2 in McCN solutions show a reductive response presumably due to copper(II)-copper(I) couple. Thermal study (TG-DTA) of 1 reveals a weight loss of 9.21% at 70-85 K corresponding to two crystalline water molecules. Structures of 1 and 2 are solved by X-ray diffraction study. Compound 1 adopts a distorted octahedral CuN2O4 environment coordinated through two N atoms of dpa and four 0 atoms of two chelating acetates with elongated axial bonds. In 2, copper(II) is ligated by four N atoms of two dpa units and two 0 atoms of an acetate in chelating fashion resulting a cationic core of [Cu(OAc)(dpa)21(+.). Crystal packings show that mononuclear units of 1 self-assemble through cooperative hydrogen bonds and pi center dot center dot center dot pi interaction and of 2, through hydrogen bonds along with C-H center dot center dot center dot pi interaction leading to 2D sheets. Both the complexes show high-energy intraligand (1)(pi center dot center dot center dot pi*) fluorescence and intraligand (3)(pi center dot center dot center dot pi*) phosphorescence in glassy solutions (DNIF at 77 K). (C) 2007 Elsevier B.V. All rights reserved.